If you wish to live in a one bedroom flat then 650KWD atleast (not furnished) will cost in rents and two bedroom starts with 700KWD
If you have two children and your wife is a stay home mother then its a bad news for you because your kids school fee alone will cost you 250 each and this is the least and there are other activities your ward would like to participate in too so you must leave a good 100KWD aside .
Transportations bills arent cheap either you must spend 30-50KWD on petrol every month and if you havnt noticed the hidden speed limit cameras, your in for a very big surprize because penalties here arent that cheap let alone forgetting to wear your seat belts and your phone on your ear while you are driving. You must have spare money always incase of a major car crash because car repairs alone can cost you 300-500KWD.
Food and clothing for a family may cost 200-250KWD. This includes eating out. Theres health insurance and residency fee (for migrants) that i havnt mentioned yet because the above must have already scared the day lights out of you. You can forget saving for going back home or building a house for you family back home because you have spent all you blood money living in Kuwait.